In the first year of the second world war a tribunal heard evidence about a "fine young man", a Methodist Sunday school teacher and Cambridge graduate, whose conscience forbade him to take up arms.

He was my father, Richard Wainwright, and the hearing's ruling in his favour led to six years' work with the Quaker-run Friends' Ambulance Unit (FAU), from cleaning hospital bedpans in Gloucester to saving German families and refugees from reprisals after the allied victory.

His pacifist war service will be recognised this weekend with that of more than 1,300 colleagues in the FAU, 17 of them killed in action, and their counterparts in the Friends Relief Service (FRS) which helped civilian victims of war, first in the 1940-41 blitz and then overseas in the wake of the fighting.

Four simple curves of Rutland limestone with benches resembling a Quaker meeting place stand in a quiet grove of trees on the fringe of the National Memorial Arboretum in Staffordshire. It is a remarkable venture; Quakers are so uncomfortable with earthly show that many of their burial grounds have no headstones and even a man as exceptional as Joseph Rowntree shares the modest curved marker common to all graves in the Friends' cemetery at York.

The choice of the National Memorial Arboretum adds to the surprise. As the trustees of the new memorial say, "some Quakers may initially feel out of their comfort zone here". The site is largely filled with tributes to men and women who died on armed service, and has many military emblems.

"This has led to a lot of discernment," says Anthony Wilson, clerk to the Quaker Service Memorial Trust. He uses the distinctive term for the way that Friends reach agreement, sifting pros, cons and reasons behind attitudes, quietly, always without a vote. "Wouldn't a bench or a tree do?" asked some from the UK's 70 Quaker area meetings when first informed of the £65,000 cost (minus 20% VAT, which the Quakers will get back).

"Then they saw just how many trees and benches the arboretum already has," says Wilson. There are thousands, and almost all are in memory of armed service. The trust wanted something distinctive but not showy and was encouraged in this by the arboretum, which is conscious that too many "samey" memorials risk dulling both the landscape and visitors' feelings.

Indeed, they were asked for something "iconic" – a very un-Quaker word. But Friends were reassured by the warmth of the Royal British Legion, which manages the park in the spirit of its founding aim to be "a place of joy where the lives of people would be remembered … in a world of peace". Alongside the regimental sites are moving memorials to first world war "deserters" shot at dawn, and the allied bombing of Dresden, which killed as many as 25,000 civilians.

A convoy of the Friends' Ambulance Unit in north Africa in 1942 .

The clincher for many, however, was the fortuitous appearance of a Manchester academic, Jenny Carson, and her doctoral thesis on the FRS, which has led to a portable exhibition linked to the memorial, where Quaker beliefs and work are explained. This fulfilled the strong sense that remembering would be valuable, and the memorial acceptable, if they informed contemporary Quaker work.

They do. Parallels between Europe's horde of "displaced persons" in 1945 and today's asylum seekers are extraordinarily close. Not allowed to work, given little or no say over where to live, and regarded with intense suspicion – these were all evils that my father encountered in his work with displaced persons. He had a Leveson moment too. Commissioned to write a "chatty piece" on displaced persons by Chatham House, the Royal Institute for International Affairs, he saw a version reprinted in the Times, with all his original qualifications and hesitations cut out. As the FAU's second-in-command in north-west Europe to Gerald Gardiner, later Labour lord chancellor, he grew skilled at providing precise, factual information, impeccably sourced, to the media, politicians and allied occupation staff.

His experiences are mirrored in records from other "conchies", as the conscientious objectors were known; some still living (a score or so are expected to attend the opening ceremony), others alive in family letters and memories, recorded interviews and reminiscences contributed to the Quaker archive at Friends' House, and the BBC's online archive, WW2 People's War. He seldom spoke about the dark side, apart from telling my mother about an atrocity where Germans in a barn were blown up. But other details slipped out.

The hospital at Gloucester, for example, had a medical orderly so hostile to FAU "cowards", as he called them, that he took unnecessary blood samples and then bragged about using them to feed his tomatoes. Such bullying was nothing compared with the brutality shown to conscientious objectors in the first world war. As a boy, my father knewof their cells at Richmond castle, in Yorkshire, a family picnicking spot, which have since become a moving museum. But the stigma was lifelong; canvassing for him during his 17 years as a Liberal MP, I regularly had to deal (very robustly) with doorstep sneers about "cowardice".

There were happier memories – notably Christmas Eve 1944, in a billet at the chateau of a French marquis. My father and another non-Quaker colleague were so put out by the lack of seasonal festivity (if Friends have a vice, it may be excessive gravity) that they put up notices saying: "Quakers! It is the season of joy and good cheer!" It was a shame that his particular ambulance column did not include Donald Swann of the comedy duo Flanders and Swann, who was also an FAU volunteer. But George Fox, the Quakers' founder, would surely not have minded the tease. Part of his injunction to Friends to "walk cheerfully over the world, answering that of God in others" is among the hand-carved inscriptions on the memorial, alongside the citation for the Nobel peace prize given to the Quakers in 1947 when the work of the FAU and1 FRS was fresh and well-known.